Transparent charge-carrier transport layers, that is to say, transport layers for electrons or holes, play a crucial role in many applications in large-surface opto-electronics, especially in displays, touchpads or solar cells. To an increasing degree, charge-carrier transport layers contain organic materials, particularly in the case of organic light-emitting diodes (OLEDs) and organic solar cells. The advantage of organic materials, especially of polymers, is that they can be processed out of the liquid phase and therefore allow the vacuum-free—and thus cost-effective—production of large-surface electro-optical elements.
As a rule, radiation-emitting components, especially organic light-emitting diodes (OLEDs), have a hole transport layer and often also an electron transport layer. In spite of an internal quantum efficiency of up to 100% for the conversion of electron-hole pairs into photons, if no additional measures are taken, the total reflection inside the radiation-emitting component allows only about 20% of the light to reach the outside, where it can then be further utilized.
British application GB 2 426 627 A describes a light-emitting component that contains a light-absorbing layer in which metallic nanocrystalline particles having a mean size of 2 nm to 20 nm have been incorporated into a matrix.
German patent application DE 101 64 016 A1 describes an organic light-emitting diode (OLED) with an organic charge-carrier transport layer that comprises at least two partial areas that differ in terms of their index of refraction. In this context, the at least two partial areas are made up of different polymers which form a composite-like structure owing to different degrees of cross-linking or of molecular branching, and to different densities or copolymerization of the various polymers.
German patent application DE 10 2007 006 348 A1 describes a light-emitting component that contains a substrate or a layer which—relative to the emitter layer—is adjacent to the substrate on the outside, and into which scatter particles having a size ranging from 1 nm to 10 μm have been incorporated. Nanoparticles made of gold, silver, platinum, nickel, copper or polystyrene are employed as the scattered particles, whereby the scatter particles preferably have a nucleus area and a shell.
U.S. patent application 2007/0176174 A1 describes a conductive polymer for electro-optical devices which comprises SiO2 or TiO2 nanoparticles having diameters ranging from 5 nm to 100 nm. Preferably, a PEDOT:PSS derivative is used as the conductive polymer.
U.S. patent application 2008/135809 A1 describes conductive polymers for OLEDs, whereby the conductive polymers comprise PANI or PEDOT, wherein nanoparticles, especially SiO2 or Nafion nanoparticles having a size of less than 1000 nm, have been incorporated.